Formerly there were those who said: You believe things that are incomprehensible, inconsistent, impossible because we have commanded you to believe them; go then and do what is unjust because we command it. Such people show admirable reasoning.Truly, whoever is able to make you absurd is able to make you unjust. If the God-given understanding of your mind does not resist a demand to believe what is impossible, then you will not resist a demand to do wrong to that God-given sense of justice in your heart. As soon as one faculty of your soul has been dominated, other faculties will follow as well. And from this derives all those crimes of religion which have overrun the world.
"Questions sur les miracles (1765)"

Virtue supposes liberty, as the carrying of a burden supposes active force. Under coercion there is no virtue, and without virtue there is no religion. Make a slave of me, and I shall be no better for it. Even the sovereign has no right to use coercion to lead men to religion, which by its nature supposes choice and liberty. My thought is no more subject to authority than is sickness or health.